Question: Which of these numbers is composite? ${2,\ 35,\ 43,\ 53,\ 61}$
Solution: A composite number is a number that has more than two factors (including 1 and itself). 2, 43, 53, and 61 each have only two factors. The factors of 35 are 1, 5, 7, and 35. Thus, 35 is the composite number.